Year	Percent change (Units)
1980	32.203
1981	13.698
1982	4.830
1983	1.965
1984	2.447
1985	3.016
1986	1.390
1987	6.050
1988	7.185
1989	5.069
1990	9.337
1991	9.251
1992	4.458
1993	5.800
1994	5.568
1995	4.754
1996	4.925
1997	6.574
1998	3.965
1999	1.355
2000	2.779
2001	3.164
2002	3.733
2003	3.420
2004	3.035
2005	2.618
2006	2.090
2007	3.606
2008	4.139
2009	2.801
2010	3.034
2011	4.158
2012	1.426
2013	1.143
2014	0.833
2015	1.132
2016	1.338
2017	1.407
2018	1.320
2019	0.738
2020	0.613
2021	3.698
2022	5.017
2023	3.158
2024	2.200
2025	2.000
2026	2.000
2027	2.000
2028	2.000
2029	2.000